PHARMACOLOGICAL ACTION:CARDIBLOK is a non-selective beta-adrenergic blocking agent, and reduces cardiac activity by diminishing or preventing beta-adrenergic stimulation. It reduces the rate of contraction and the cardiac output, and prolongs A-V conduction time. In response to the inhibition of the beta-adrenergic-receptors the cardiac oxygen requirement diminishes. The blood pressure in hypertensive patients is also reduced.

CONTRA-INDICATIONS:CARDIBLOK is contra-indicated in patients with any of the following:
Bronchial asthma or bronchospasm
Metabolic acidosis (e.g. in diabetes)
Atrioventricular block
Marked bradycardia (less than 50 beats per minute)
Heart failure refractory to digitalis
UraemiaPregnancy and lactation
Hypoglycaemia
Raynaud's phenomenon
Patients suffering from peripheral vascular disease
Particular caution should be exercised with patients suffering from the following: bronchitis, chronic respiratory diseases and second and third degree heart block. In the pre-operative period it is generally unwise to reduce the dosage to which the patient is accustomed, as there may be danger of aggravation of angina pectoris or of hypertension. A patient's normal tachycardiac response to hypovolaemia or blood loss may be obscured during or after surgery. Particular caution should be taken in this regard.

WARNINGS:Bronchospasm may occur, particularly in susceptible individuals. CARDIBLOK contains Tartrazine which may cause allergic-type reactions (including bronchial asthma) in certain susceptible individuals. Although the overall incidence of Tartrazine sensitivity in the general population is currently thought to be low it is frequently seen in patients who also have aspirin sensitivity.

DOSAGE AND DIRECTIONS FOR USE:Tablets should preferably be taken before meals. Dosage is largely determined by the response of the patient. In most conditions, treatment should begin with a small dose which should be gradually increased.
The most usual doses are 20 mg to 40 mg three or four times a day. The dose may be increased up to 320 mg daily in the treatment of hypertension. In phaeochromocytoma, 60 mg daily should be given for 3 days pre-operatively. The normal dose should be reduced in elderly patients, or in patients suffering from renal dysfunction, as adverse effects are more common in these patients.
If symptoms of weakness or faintness occur, treatment should be withdrawn temporarily and started again at a lower dose which may be increased very slowly.
Abrupt discontinuation of therapy may cause exacerbation of angina pectoris in patients suffering from ischaemic heart disease. Discontinuation of therapy should be gradual and patients should be advised to limit the extent of their physical activity during the period that the medicine is being discontinued.

SIDE-EFFECTS AND SPECIAL PRECAUTIONS:The most common side-effects of CARDIBLOK are gastro-intestinal such as nausea, constipation, vomiting and diarrhoea. Fatigue and dizziness may also occur. Central nervous system effects include depression, hallucinations and disturbances of sleep and vision, vivid dreams, nightmares, paradoxical hypertension, confusion, overt psychosis, allergic reactions, transient hearing loss, metabolic disturbances, alopecia, myopathies, dry eyes, stomatitis, malaise may also occur. Cardio-vascular effects include bradycardia, congestive heart failure, heart block, hypotension, cold extremities and paraesthesia.
Development of Raynaud's phenomenon (due to unopposed arteriolar sympathetic activation), sexual impotence, hypoglycaemia, skeletal muscle weakness and gastro-intestinal disturbances may occur. Severe peripheral vascular disease and even peripheral gangrene may be precipitated.
Administration to pregnant mothers shortly before giving birth, or during labour may result in the newborn infants being born hypotonic, collapsed and hypoglycaemic. Blood disorders and skin rashes may also occur. Other side-effects reported include fluid retention and mass gain, muscle cramps and dry mouth.
In congestive heart failure, CARDIBLOK should only be administered when the patient is fully digitalised and then only with great caution. This combination can be considered despite the potentiation of negative chronotropic effect of the two medicines. Careful control of dosages and the individual patient's response (and notably pulse rate) is essential in this situation. Adverse reactions are more common in patients with renal decompensation. In diabetes mellitus CARDIBLOK may reduce blood-sugar levels and may enhance the effects of hypoglycaemic agents. Great care should be exercised in giving CARDIBLOK to patients undergoing anaesthesia and myocardial depressants such as chloroform or ether must be avoided CARDIBLOK may mask the symptoms of hyperthyroidism. CARDIBLOK should never be given to patients with phaeochromocytoma without concomitant alpha-adrenergic blocking therapy.

Interactions:It can be dangerous to administer this medicine concomitantly with the following medicines: hypoglycaemic agents, phenothiazines and various anti-arrhythmic agents. The effects of other myocardial depressant agents such as quinidine, procainamide and lignocaine may be enhanced by CARDIBLOK. CARDIBLOK should not be used with verapamil and neither compound should be administered within several days of discontinuing the other. It should be used with caution in the case of other calcium antagonists. Caution should be used when transferring a patient from clonidine onto a beta-blocker as this may result in a hypertensive crisis. If CARDIBLOK and clonidine are given concurrently, the clonidine should not be discontinued until several days after the withdrawal of CARDIBLOK as severe rebound hypertension may occur. The effects of CARDIBLOK are diminished by beta-adrenergic stimulating agents; the hypotensive effects of CARDIBLOK may be dangerously reversed and the peripheral vasoconstrictor effects enhanced by alpha-adrenergic stimulating agents such as noradrenaline or those mixed with alpha- and beta-adrenergic stimulating properties such as adrenaline. The effects of CARDIBLOK may be enhanced by adrenergic neurone blocking agents such as guanethidine, bethanidine or reserpine and the hypotensive effects by diuretics. CARDIBLOK may enhance some of the cardiac effects of digitalis and diminish others.

KNOWN SYMPTOMS OF OVERDOSAGE AND PARTICULARS OF IT'S TREATMENT:Excessive bradycardia, severe hypotension, bronchospasm and heart failure may be produced in certain individuals. Patients with mild overdose should be observed for at least 4 hours, as apnoea and cardiovascular collapse may appear suddenly. Gastric lavage should be performed within 4 hours of suspected overdose. Activated charcoal is necessary in severe overdose. Atropine may be used to treat bradycardia. If the response is inadequate, glucagon may be given intravenously. Alternatively, dobutamine or isoprenaline may be used for the management of hypotension. Large doses of isoprenaline may be required to counteract the beta-blockade. Transvenous cardiac pacing may be required for severe bradycardia. Bronchospasm should be treated by the intravenous injections of aminophylline or by the inhalation or intravenous injection of a selective beta-2-stimulant. Further treatment is symptomatic and supportive.